Derivative Instruments - Changes in AOCI (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ (52,124)
Ending balance	(56,428)	$ (52,124)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	206	32
Net unrealized loss on cash flow hedges	(567)	(27)
Reclassification of net realized loss on cash flow hedges into current operations	398	201
Ending balance	$ 37	$ 206